Synchros and servosystems are error detection systems which play an important part in the operation of control systems having broad military and commercial application. These systems can be catalogued according to speed or accuracy as single or two-speed. The latter typically comprises a coarse system which is energized when the error is larger than a predetermined amount; and a so-called fine system which takes over when the error signal is small. The "single" servo system is typically only a coarse system for use in applications where accuracy is not paramount.
In the military, single speed systems include airborne instrumentation indicator units for such purposes as compass heading, radar altitude, mach air speed, roll/pitch attitude, rate of climb, turbo speed (TACH) and engine temperature. Dual speed systems find use in altimeters where relatively, extreme accuracies are required, e.g., altimeters.
Heretofore, converters of DC to AC ARINC voltages involved first the modulation of the DC signals representing the sine and cosine of the angle being detected; then the resolving of the modulated signals followed by demodulating the resolved signals; and, finally the amplifying of the demodulated signals to a level sufficient to power a servo driver. This involved, by comparison to the herein disclosed design, relatively complex circuitry with approximately twice as many components.
Further, prior designs required each function in the process to be operated at the same frequency, normally the aircraft or vehicle operating frequency, necessitating synchronization. Interactive reactions between portions of the system are commonplace. These result in erratic performance and reduced accuracy, often in critical applications.
It is, therefore, a primary object of the present invention to provide a DC sine/cosine position servo system which utilizes approximately 50% less components over present systems.
It is another object of the invention in one embodiment, to provide a single speed, position servo system wherein the position error is reduced to .+-.15 minutes.
It is still another object of the present invention to provide a servo arrangement which can be employed as part of a two speed sine/cosine, attitude indicating, system wherein an error of .+-.5 feet in 100,000 feet can be obtained.
It is yet another object of the invention to provide a DC sine/cosine system where a different operational frequency can be employed, separate from the aircraft or system frequency, thereby eliminating detrimental, interactive effects.